This invention relates to a cylindrical roller bearing that receives an axial load.
The cylindrical roller bearing has races, which are an outer race and inner race, and formed with a rib, or provided with a separate guide rib adjacent it.
When the cylindrical roller bearing while it rotates receives an axial load, large friction occurs when localized stress, such as edge loading, acts in the area where the end surface of the cylindrical rollers comes in contact with the guiding surface of the rib (or guide rib) of the races. At high-speed rotation, this friction becomes evident and there is a possibility that it could promote wear and result in early damage to the bearing.
Therefore, in order that the contact stress is as uniform as possible, the opposite end surfaces of the cylindrical rollers and the guiding surface of the rib of or for the races are formed with a slight taper or curvature referred to as crowning, so that large edge loads do not occur.
For example, as disclosed in British Patent No. 1520060, crowning is performed on the guiding surface of the rib in a cylindrical roller bearing, so that the end surface of the cylindrical rollers does not come in contact with the end edge in the radial direction of the guiding surface of the rib, so that an oil film is effectively formed on the area of contact.
Also, in Japanese patent publication Jitsu Ko Sho No. 59-13369, as shown in FIG. 7, the guiding surface (Ff) of the rib, for example of the inner race (N), in a cylindrical roller bearing, is given an outward opening taper that has a certain angle (xcex1), and the end surface (Fr) of the roller that comes in contact with it is given a crown shape.
However, in this kind of prior art cylindrical roller bearing, although crowning is performed on the guiding surface of the rib in the bearing, or although the contact between the guiding surface of the rib of or for the inner race and the end surface of the rollers is formed such that a conical shaped outer diameter surface, that is the guiding surface of the rib of inner race, which has the apex (Ap), comes in contact with a spherical surface, that is the end surface of the rollers as shown in FIG. 7, the direction of the major axis of the contact ellipse (Ac), as shown in FIG. 8, that is formed at the area of contact between the roller and rib is in the radial direction (y) of the inner race (N) of the bearing, and depending on the size of the axial load, this contact ellipse (Ae) protrudes from the relief groove (Nm) of the guiding surface (Ff) of the rib or from the outer diameter or the guiding surface (Ff) of the rib, and there is a problem that an edge load will occur at the boundary surface between the contact ellipse (Ac) and the relief groove (Nm), or at the boundary surface between the contact ellipse (Ae) and the outer diameter of the guiding surface (Ff).
Also, when the center of the contact ellipse (Ae), which is the contact surface between the roller and the rib, is raised to the outer diameter side of the guiding surface (Ff), in order to prevent the contact ellipse (Ae) from protruding from the relief groove (Nm) of the guiding surface (Ff), sliding between the roller and rib would become large, the amount of heat generated would increase, the temperature rises in the bearing, and scuffing and seizure in the rib would occur.
In order to remove the problems, still not solved, in this kind of prior art cylindrical roller bearing, an objective of this invention is to provide a cylindrical roller bearing wherein the major axis of the contact ellipse, that is formed at the area of contact between the end surface of the cylindrical rollers and the guiding surface of the rib of or for the inner race, is directed in the circumferential direction of the inner race of the bearing, so that it is difficult for protrusion and edge loading to occur at the area of contact between the guiding surface of the rib and the end surface of the rollers when an axial load is applied to the cylindrical roller bearing.
An other objective of the present invention is to provide a cylindrical roller bearing wherein the major axis of the contact ellipse of the sliding contact area between the guiding surface of the rib of or for the inner race and the end surface of the cylindrical rollers is directed in a specified direction, so that the edge load that might occur when the contact area between the rib and the cylindrical rollers protrudes from the end surface of the rollers or from the guiding surface of the rib is reduced, thereby effectively preventing damage to the cylindrical rollers and the inner race.